What you need to know about macular degeneration

Macular degeneration (AMD) is the leading cause of blindness among elderly Canadians. Close to 80,000 Canadians are diagnosed with AMD annually. Here are the facts.

• Roughly the size of an eraser on a pencil, your macula occupies the centre of the retina in your eye. Despite its small size, it is responsible for the sharp, high-definition, central vision that allows you to read, drive, recognize faces and distinguish fine details.
• When you have macular degeneration, it means that the macula in one or both eyes has broken down irreversibly over time. Your vision may become blurred, a blind spot may develop in the centre of your visual field and many fine-detail activities—such as reading and writing—may become difficult or impossible to do with your accustomed ease. Your peripheral vision, however, remains intact.

No one knows what causes age-related macular degeneration, but by some estimates it accounts for one-third of all cases of vision loss in Canada.

Dry (or nonexudative or atrophic) form: Nearly 90 percent of those with AMD have this form, in which the light-sensitive cells in the macula slowly decay, and yellow spots of fatty deposits called "drusen" appear on the macula. Dry AMD is the less severe of the two forms, progressing slowly and sometimes stabilizing temporarily. You might not even notice symptoms of vision loss, especially if it's restricted to one eye and your "good" eye compensates.

Wet (or exudative or neovascular) AMD: In the less common form, fine blood vessels grow beneath the retina, leaking and damaging the macula. Wet AMD progresses more quickly than dry AMD and it causes more severe vision loss—sometimes within days or weeks. If left untreated, wet AMD can lead to legal blindness (defined as vision of 20/200 or worse), although not to total blindness. About 15 percent of people with the more common dry AMD go on to develop wet AMD.

• Although it’s rare, macular degeneration can develop in young people due to a genetic disorder, or as a drug side effect. Most often, however, it is related to the aging process.
• Your odds of getting AMD are also higher if you have a family history of it, or if you're female, white and have light-coloured eyes. Other risk factors include exposure to smoke and direct sunlight, and having a condition such as high blood pressure, high cholesterol or obesity.

• Monitor your vision for signs of change.
• For some people, daily supplements of high-dose antioxidants and zinc may help.
• Laser surgery or photo­dynamic therapy may stop certain cases of wet AMD.

• Keep up with the news about AMD: Researchers are currently testing and developing new treatments that may turn out to be just what you need. Ask your doctor about clinical trials of therapies that might help your particular case.
• Don't be afraid to use your eyes: Doing your normal activities won't make your AMD get worse. So go ahead and read, watch television and use a computer as much as you want.

• The Canadian National Institute for the Blind has undertaken public awareness campaigns about macular degeneration and offers comprehensive information about symptoms and treatment (416-486-2500 or www.cnib.ca).
• A list of Canadian low-vision specialists can be found online at www.lowvision.org.